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package filepath
import (
"regexp"
"strings"
)
var windowsAbs = regexp.MustCompile(`^[a-zA-Z]:\\.*$`)
// Abs is a version of path/filepath's Abs with an explicit operating
// system and current working directory.
func Abs(os, path, cwd string) (_ string, err error) {
if IsAbs(os, path) {
return Clean(os, path), nil
}
return Clean(os, Join(os, cwd, path)), nil
}
// IsAbs is a version of path/filepath's IsAbs with an explicit
// operating system.
func IsAbs(os, path string) bool {
if os == "windows" {
// FIXME: copy hideous logic from Go's
// src/path/filepath/path_windows.go into somewhere where we can
// put 3-clause BSD licensed code.
return windowsAbs.MatchString(path)
}
sep := Separator(os)
// POSIX has [1]:
//
// > If a pathname begins with two successive <slash> characters,
// > the first component following the leading <slash> characters
// > may be interpreted in an implementation-defined manner,
// > although more than two leading <slash> characters shall be
// > treated as a single <slash> character.
//
// And Boost treats // as non-absolute [2], but Linux [3,4], Python
// [5] and Go [6] all treat // as absolute.
//
// [1]: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13
// [2]: https://github.com/boostorg/filesystem/blob/boost-1.64.0/test/path_test.cpp#L861
// [3]: http://man7.org/linux/man-pages/man7/path_resolution.7.html
// [4]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/path-lookup.md?h=v4.12#n41
// [5]: https://github.com/python/cpython/blob/v3.6.1/Lib/posixpath.py#L64-L66
// [6]: https://go.googlesource.com/go/+/go1.8.3/src/path/path.go#199
return strings.HasPrefix(path, string(sep))
}
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